Lightning arrester or surge absorber



March 3, 1931. v. 2. DE FERRANTI LIGHTNING ARRESTER OR SURGE ABSORBER Filed Oct. 19, 1929 2 Sheets-Sheet l March 3, 1931. v. 2. DE FERRANTI LIGHTNING ARRESTER OR SURGE ABSORBER Filed Oct. 19, 1929 2 Sheets-Sheet 2 Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE VINCENT ZIANI DE FERRANTI, OF HOLLINWOOD, ENGLAND, ASSIGNOR T0 FERRANTI INC., OF NEW YORK, N. Y.

LIGHTNING ARRESTER; OR SURGE ABSORBER Application filed October 19, 1929, Serial No. 400,958, and in Great Britain November 20, 1928.

This invention relates to lightning arresters or surge absorbers and has for its object to provide improved or simplified constructions thereof particularly from the point of View of economy of insulation and minimizing of bulk.

It is well known that electrical stress is re sisted to the utmost when the direction of electrostatic lines of force is normal to the surface of the interposed insulating material. According to the present invention lightning or surge absorbers are provided in which this principle realized to the utmost.

The invention consists in a lightning or surge absorber embodying a metal casing containing a helical coil constituting a primary transformer winding, surrounding a metal core (preferably hollow cylindical) with a plurality of interposed insulating sheaths and a pair of connecting leads disposed radially or substantially so in relation to the planes of the two end convolutions respectively.

The invention also consists in a lightning or surge absorber as set forth above wherein the helical coil is of somewhat shorter axial length than the axial length of the core, a plurality of insulating discs of graded diameter being disposed on the unwound portions of the core, each disc being associated by means of an insulating collar with an insulating sheath surrounding the core.

The invention also consists in a lightning or surge absorber as set forth above wherein the electrostatic lines of force surrounding the terminal leads merge with the electrostatic lines of force between the casing and coil without sudden change of direction.

The invention also consists in lightning and surge absorbers substantially as herein after described.

Referring to the accompanying diagrammatic drawings Figure l is a vertical longitudinal sectional view of part of one convenient arrangement in accordance with the present invention; and

Figure 2 is a vertical cross sectional view thereof.

In carrying the invention into effect in one form by way of example, I provide a cylindrical metal casing a at the centre of which I mount a metal tube 6 coaxial with the longitudinal axis of the casing. This metal tube constitutes the secondary winding of :a transformer of which the primary comprises a helical coil, winding 0 surrounding the metal tube core 6. In addition to actingv as the secondary winding of a transformer the tube core 6 is the seat of eddy current losses due to its being situated in a strong part of the magnetic field from the coil. F urthermore, the tube core 7) acts as one electrode of a condenser of which the coil is the other electrode. The tube is conveniently mounted on brackets (l attached to two end plates 6 which may be detachable and around the core is placed a plurality of insulating sheaths f of gradually decreasing length, the helical coil 0 resting upon the outermost sheath.

-To the ends of the sheaths a plurality of insulating plates 9 are applied, these discs preferably being formed with flanges h which rest between adjacent pairs of sheaths. The discs are graded in diameter, the smallest diameter discs resting nearest the ends of the coil. Between each pair of plates 9 distance rings j are provided as shown. Each end is of the coil 0 is cranked so as to occupy a substantially radial position in relation to the helix and each cranked end is adapted to contact with a terminal connecting bar m fitted within a hollow insulating member 71. attached to the top of the casing near each end thereof.

The apertures provided at the top of the casing at which the said insulating members are fitted are furnished with shaped electrostatic field guard rings 0 and between these rings and the terminal connecting bar m is provided a plurlaity of insulating sheaths p of graded lengths such that concentration of electrostatic lines of force is avoided as far as possible. The insulating member a comprises a conical shaped insulator furnished with the usual petticoat exterior. The casing is filled with oil and is preferably connected to earth while the two terminals are connected so as to insert the helical coil in series with a line adapted to be protected from lightning or other electrical transience. According to the arrangement described 7 above the distribution of electrostatic lines of force is distributed in such a way that the 5 lines of force surrounding the terminal leads merge with the electrostatic lines of force between the casing and coil withoutany suddent change of direction. Furthermore the directions oi the lines of force are substan- 10 tially normal to the insulatinginaterial' pro:

Vided. Thus the latter is adapted to resist to the utmost electrical stress to which it may be subjected.

Iclaimi Y 7 a it a 15 1. A lightning or surge absorber embody ing a inetal casing containing a helical coil constituting a primary transformer Windiiig; surrounding metal core (preferably hollow cylindrical) with a plurality of inter- 2Z posed insulating sheaths anda pair of connecting leads disposed radially or substantially so in relation tothe planes of the two end 'c'oiii'rolutidns respectively.

2. A lightning or surge absorber as claimed 5 in claim 1 wherein the helical coil is of somewhat shorter axial length than the axial length of the core, a plurality of insulating discs of graded diameter being disposed on the unwound portions of the core, each disc beingassbciated by means of an insulating collar with an insulating sheath surroundj 3; light ing or surge absorber as claimed in claim 1 Whereinthe electrostatic lines of '35 force surrounding the terminal leads merge with the electrostatic lines of force between the casing aiid coil Without sudden change 7 of direction. in r I In testimony whereof I have signed my g; name to this specification.

VINCENT ZI-ANI DE FERRANTL r uv.) 

